[Ada] Use GNAT encodings only when -fgnat-encodings=all is specified

[Ada] Use GNAT encodings only when -fgnat-encodings=all is specified

gcc/ada/

	* gcc-interface/decl.c (gnat_to_gnu_entity) <discrete_type>: Add a
	parallel type only when -fgnat-encodings=all is specified.
	<E_Array_Type>: Use the PAT name and special suffixes only when
	-fgnat-encodings=all is specified.
	<E_Array_Subtype>: Build a special type for debugging purposes only
	when -fgnat-encodings=all is specified.  Add a parallel type or use
	the PAT name only when -fgnat-encodings=all is specified.
	<E_Record_Type>: Generate debug info for the inner record types only
	when -fgnat-encodings=all is specified.
	<E_Record_Subtype>: Use a debug type for an artificial subtype only
	except when -fgnat-encodings=all is specified.
	(elaborate_expression_1): Reset need_for_debug when possible only
	except when -fgnat-encodings=all is specified.
	(components_to_record): Use XV encodings for variable size only
	when -fgnat-encodings=all is specified.
	(associate_original_type_to_packed_array): Add a parallel type only
	when -fgnat-encodings=all is specified.
	* gcc-interface/misc.c (gnat_get_array_descr_info): Do not return
	full information only when -fgnat-encodings=all is specified.
	* gcc-interface/utils.c (make_packable_type): Add a parallel type
	only when -fgnat-encodings=all is specified.
	(maybe_pad_type): Make the inner type a debug type only except when
	-fgnat-encodings=all is specified.  Create an XVS type for variable
	size only when -fgnat-encodings=all is specified.
	(rest_of_record_type_compilation): Add a parallel type only when
	-fgnat-encodings=all is specified.